Selecting an Electrical Temperature Transmitter for mobile working machines such as tractors, harvesters, bulldozers, backhoes, mining machines, forklifts, and industrial trucks work day in and day out under extremely harsh conditions. It is important to monitor the temperature of their systems to prevent downtime and ensure continued performance.

Resistive temperature detector (RTD’s)

There are primarily two types of temperature measurement technologies for mobile working machines. The first is using a resistive temperature detector (RTD’s) and is based on the principle that the electrical resistance of a metal increases as temperature increases. By using this relationship a temperature measurement can be inferred by measuring the resistance of the RTD element. The problem with this measurement technique is that the temperature to resistance relationship must be stored in the machines computer and when replacing the RTD probe during field repairs, the same RTD element must be used or the relationship will not be valid, resulting in temperature errors and poor machine operation.

Temperature Transmitter

The second temperature measurement technology that eliminates some of the inherent problems of using a plain RTD sensor is a temperature transmitter. A temperature transmitter combines a temperature sensor (an RTD for example) and a transmitter in the same instrument. The RTD measures the temperature while the transmitter amplifies and transmits the signal to a controller or computer system. The advantage a temperature transmitter has over just using an RTD sensor is that it converts the temperature measurement into a known current or voltage signal that is proportional to the temperature being measured.

Another advantage is that when different parameters are being measured on mobile working machines, the output from the different instruments can be rationalized into a common interface such as 4-20 mA or 1-5 V so all devices are communicating in the same language. In most industries, transmitters are becoming intelligent instruments largely because they are microprocessor based. Most of these devices are now regarded as “smart” devices that can be programmed to achieve a desired result. The WIKA model TR33 temperature transmitter for mobile working machines is one such device. The transmitter contains an EEPROM that can be programmed to changing conditions on the machine. Using WIKA’s free software developed specifically for the model TR33, the customer can adjust measuring range, temperature units, damping, fault signals, interference immunity and device TAG number. The fault signal feature is especially useful for mobile working machine manufactures. By defining a predefined fault signal field technicians can quickly identify if the transmitter needs to be replaced by reading the output signal of the transmitter.

The predefined fault signal also prevents field technicians from replacing good working transmitters until a problem can be identified. By using the model TR33 temperature transmitter with fault signal capability the machine manufacture can reduce warranty costs associated with the time to repair the machine and the age old practice of replacing easily serviceable or suspect components in an effort to get machines back into service. For mobile working machines that operate in explosive or hazardous atmospheres like mining machines, WIKA created the model TR34 temperature transmitter. It contains all the features and capabilities of the model TR33 but with the added benefit of being intrinsically safe. All WIKA temperature transmitters come in a variety of process connections; stem insertion lengths and diameters, and electrical connectors that you can be sure you will find a temperature transmitter that fits your design needs. WIKA offers full lines of probes, switches, and transmitters to measure engine, transmission, hydraulic, cooling and other system temperatures in mobile machinery. Give the temperature transmitter experts at WIKA a call and let them walk you through the selection process. They’ll make sure you’ve got the right temperature transmitter for the job. WIKA: We’re Not Just Pressure Gauges.

Learn more about WIKA products in Mobile Machines here.


Wheel loader excavator with backhoe unloading clay

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